The Internet's core bandwidth continues to double every year. Some of this additional bandwidth is consumed as more and more users access the Internet. Other additional bandwidth is consumed as existing users increase their use of the Internet. This increase of Internet use translates into an increase in traffic directed to and from World Wide Web (WWW) servers and other Internet servers.
Replacing a WWW server with a WWW server of twice the capacity is a costly undertaking. Adding additional WWW servers is less costly but generally requires a load-balancing mechanism to balance workload so that each virtual server performs work proportional to its capacity and the number of servers available to the traffic management device that is performing the load balancing.
Traffic across the Internet typically comes in the form of Transmission Control Protocol/Internet Protocol (TCP/IP) packets. TCP/IP has many layers for addressing packets. Managing TCP/IP packet traffic using lower layers typically requires less processing than managing packets using higher layers. As a result, lower layer traffic management may often be done in hardware with its attendant speed. Unfortunately, managing packet traffic based on lower layer information is typically not flexible enough for many applications using the Internet. For example, when a user is shopping for items on a WWW server and filling a “shopping cart,” a traffic management device that sends one of packets from the user to one WWW server and another packet from the user to another WWW server may cause shopping cart information to be lost. As a result, a traffic management device may be required to store state information about connections and look at higher TCP/IP layers to maintain connections between servers and users.
This requirement for more sophisticated traffic management requires more processing. With a sufficient rate of requests, eventually a traffic management device may not be able to process traffic in a timely manner.